Active Visual Search can be either addressed as a pure exploration task [1]}, [2]} where target detection is merely subordinate to the solution of such task, or as an exploration and search task with target-specific inferences [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}. One early example of the latter approach is indirect search [3]}, [4]}, [13]} which exploits intermediate objects (e.g. a table) to restrict the search area for the target object (e.g. a telephone). Although intermediate objects are usually easier to detect because of their size, their spatial relation w.r.t. the target may be not systematic.
A softer reasoning is proposed in [13]}, where the likelihood of the target increases when objects which are expected to be co-occurring are detected. Such probabilistic modelling in a voxelised 3D scene representation is a common strategy to facilitate the planning of the agent's path towards the discovery of the target [5]}, [16]}, [17]}, [6]}, [7]}, enriched by visual attention principles [20]} that rank the search locations depending on their saliency.
